Betsy Blair, already a founding producer with Garance Films, briefly set about acquiring the rights to the original novel with the intent on making it her directorial debut. She instead sacrificed this ambition for love of director Karel Reisz, marrying and starting a new life with him in London. She abandoned the idea of directing all together.

Michael Gough is said to play the Mad Monk in the credits but he is nowhere to be seen at all in the film.

This had several major location changes. Originally to film in France, a nationwide strike caused the producers to move to Austria. The Russian invasion of Czechslovakia then meant that the production was moved to Italy, where it filmed 50 miles outside of Rome.

The film was not a box-office success, although John Huston noted in his autobiography, An Open Book, that it was highly praised in France, where there was a greater understanding of the historical context.

Oswald Morris in his memoirs says he was offered the DOP job.

Filming in Austria was delayed for 3 days by the Russian invasion of Czechslovakia in 1968.

Originally set up in 1964 as a directing vehicle for Delbert Mann.